Augmented Spark Gap Ignite r For Propellants
07 January, 2012
This is a schematic, parts list and description of a DC augmented spark gap ignition system for firearm
propellants which is capable of igniting all types of propellants when used with a breech-plug type
igniter as described elsewhere.
WARNING!! This circuit produces high voltages and currents which can shock, burn or even cause
sudden death. Its construction should not be undertaken by anyone who is not familiar with the safety
procedures required for working with such circuits.
Part
Descr
*Mouser Part Number
R1
R2
R3
R4
R5
C1
C2
D1
BR1
SCR
CCFL
T1
Batt
5W 200Ω Ohmite wire-wound resistor
100K 1/4W Carbon resistor
1K 1/4W Carbon resistor
100Ω 1/4W Carbon resistor
2 MΩ 1/4W Carbon resistor
120 μfd 330V Capacitor See note 1
0.068 μfd 630V Vishay pulse capacitor
3000V .25A diode
Four D1s in bridge configuration
800V 8A SCR
TDK CXA-L10A Inverter See note 2
Pulse transformer See note 3
CR123 3V Lithium Cell (or rechargeable)
588-95J200E
791-RC1/4-104JB
791-RC1/4-101JB
791-RC1/4-100JB
791-RC1/4-205JB
594-2222-383-20683
625-GP02-30-E3
576-S8008L
810-CXA-L10L
 Mouser Electronics (http://www.mouser.com) can supply most components.
Note 1: Obtain from disposable camera flash units. Many can be found on eBay or from electronic
surplus houses.
Note 2: There are two modifications required. First, the output must be floated from the input. There is
a wire jumper on the side marked 'GND' which must be removed. See photo below
Second, the output must be taken from directly across the secondary transformer windings, not from
the output capacitors. This can be done by either bridging the capacitor or by wiring directly to the
transformer.
Note 3: The pulse transformer was made by winding a primary and secondary over a plastic bobbin
containing a 10mm ferrite rod (look in eBay). I designed the custom bobbin, which you can either
machine from acetal or (even better) have it 3D-printed by Shapeways (http://www.shapeways.com).
To get this printed, download the file and then upload it to Shapeways. They will print it and send it to
you for a nominal fee.
The primary is wound with five layers of #30 enameled wire, with each layer being epoxied and
separated by either one thickness of one mil Mylar or two thicknesses of standard weight paper. The
wire ends should be soldered to the output leads and then buried into the channels in the bobbin. The
secondary is then covered and epoxied with either two layers of Mylar or four layers of paper, and then
the secondary is wound with eight spaced turns of #24 enameled wire.